The present invention relates to a gas flow guide for an aircraft jet engine thrust reverser in which a guide vane is disposed in a reverse thrust opening in the engine cowling to direct the gas flowing through the opening during reverse thrust operation.
Turbofan-type turbojet engines are well known in the art and typically comprise a fan driven at the front of the turbojet engine which directs a flow of bypass air through a duct bounded by the engine cowling on the inside and a fan cowling on the outside. The generally annular duct bounded by the engine cowling and the fan cowling may channel both the bypass flow and the primary exhaust gas flow at a downstream portion from the turbojet engine, or may channel only the bypass flow.
In aircraft on which the turbojet engine is mounted outside of the airframe structure, the fan cowling and the engine cowling are configured to form boundaries of the bypass flow duct and to provide aerodynamic outer surfaces to reduce drag.
FIGS. 1 and 2 illustrate a known pivoting door-type thrust reverser associated with the cowling of a turbofan-type turbojet engine. As illustrated in FIG. 1, the upstream portion of the cowling which defines the outer limits of the bypass flow duct and which is generally concentrically arranged about the turbojet engine (not shown) is designated as 1 and generally comprises an external cowling panel and an internal cowling panel interconnected by a frame 6. The outer surface of the external cowling panel has an aerodynamic surface over which the air external to the engine passes during aircraft flight. The inner surface of the inner cowling panel defines the outer boundary of the bypass flow duct 15 through which the bypass flow passes in the direction of arrow 14.
The cowling also comprises a thrust reverser and a downstream cowling portion 3. The thrust reverser comprises a door 7 pivotally attached to the cowling so as to pivot about transverse axis 20 such that it is movable between a closed, forward thrust position, illustrated in FIG. 1, and an open, reverse thrust position, illustrated in FIG. 2, in which the forward end of the thrust reverser door 7 is moved outwardly from the cowling, while a rear portion is moved inwardly into the bypass flow duct so as to redirect at least a portion of the bypass flow through an opening in the cowling in a direction that has a reverse thrust component.
A known actuator for moving the door 7 between its forward thrust and reverse thrust positions may comprise a hydraulic cylinder extending through and mounted to the frame 6, and having an extendible and retractable piston rod connected to the thrust reverser door 7.
The thrust reverser door 7 has an inner door panel or inner surface 11 and the forward end of the door 7 may have a baffle 13 to maximize the efficiency of the thrust reverser when the door 7 is in the reverse thrust position. The inner surface 11 tapers toward the outer surface of the door 7 at the forward end of the door, forming cavity 18 when in the forward thrust position.
A plurality of thrust reverser doors 7 may be incorporated into the cowling, such doors being circumferentially spaced around the periphery of the cowling. A portion of the cowling extends axially between a forward part and a rear part of the cowling adjacent thrust reverser doors 7 to provide structural rigidity to the cowling and to provide pivot mounting points for attaching the doors 7 to the cowling. French Patents 1,482,538 and 2,030,034 illustrate typical, known thrust reversers.
U.S. Pat. No. 3,605,411 discloses a pivoting door-type thrust reverser in which the baffle mounted to the upstream or forward end of the thrust reverser door is movable to an extended position when the door is in the reverse thrust position.
French Patent 2,618,853 discloses a thrust reverser in which the baffle is retracted when the door is in its forward thrust position to optimize engine performance.
In some applications, as illustrated in FIG. 1, the baffle 13 projects from the inner panel 11 of the thrust reverser door 7 even when the door is in its forward thrust position without extending into the bypass flow duct. This forms a cavity 18 facing inwardly into the bypass flow duct which will slightly degrade engine performance.
French Patent 2,680,547 discloses a thrust reverser having a combination of spoilers and baffles to attempt to optimize the direction of exhaust flow.
A deflector 8 extends from the portion of the cowling forming the forward edge of the reverse thrust opening and may have a curved distal end portion, as illustrated in FIGS. 1 and 2, or may be planar in configuration, as illustrated in FIG. 3. The curved deflector 8 illustrated in FIGS. 1 and 2 permits better gas flow during reverse thrust operation to thereby achieve an optimal effective cross-sectional length P in the reverse thrust mode. However, this design incurs aerodynamic losses degrading the performance of the engine when the thrust reverser door 7 is in the forward thrust position, because the gases in the annular duct 15 are guided into the cavity 18. The planar deflector 8 illustrated in FIG. 3 minimizes these losses since the planar configuration covers a portion of the cavity 18 to thereby reduce the disturbances in the gas flow.
However, using such a deflector reduces the effective cross-sectional length P during reverse thrust operation, since the gas passing through the reverse thrust opening is no longer guided by the curved deflector edge. In order to achieve the same effectiveness in the flat deflector as with a curved deflector, the distance between the deflection edge and the inside surface 11 of the door 7 making contact with the reverse thrust gases must be increased. However this solution causes additional problems in that the pivot axis 20 must be shifted more towards the rear of the cowling thereby increasing the axial length of the inner surface 11 extending forwardly of the pivot axis 20. The increase of this distance also increases the forces acting on the door by the pressurized gases within the gas flow duct 15 which tend to urge the thrust reverser door 7 away from the forward thrust position.